Conventionally, a step of manufacturing a sealed battery includes an inspection of sealability of a battery case for the purpose of, for example, prevention of degradation of battery performance caused by infiltration of moisture into the battery case.
In the step of manufacturing the sealed battery, a detection gas (e.g., a helium gas) is introduced into the battery case to check whether the detection gas leaks from the battery case or not.
For example, JP 2002-117901 A discloses a technique for introducing the detection gas.
According to JP 2002-117901 A, a pouring nozzle connected to a helium-supplying means through an electrolyte pot is inserted into a pouring hole, and thereafter a helium gas is discharged from the outside to the inside of a battery can (a battery case) to introduce the helium gas into the battery can.
In the step of manufacturing the sealed battery, a gas such as hydrocarbon is generated by, for example, decomposition of an electrolyte solution during an initial charge of the battery. In the step of manufacturing the sealed battery, if the gas is generated during the initial charge in such a large amount that pressure-resistance requirement of the battery can is not satisfied, the gas accumulating in the battery can needs to be released.
In this case, in the step of manufacturing the sealed battery, the initial charge is performed after temporarily sealing the pouring hole, and then the temporary seal of the pouring hole is removed to release the gas generated during the initial charge. Thereafter, a helium gas is introduced, and the pouring hole is finally sealed.
The technique disclosed in JP 2002-117901 A includes introducing the helium gas into the open battery can from the outside. In other words, the technique disclosed in JP 2002-117901 A presupposes that the pouring hole is not temporarily sealed or that the temporary seal is previously removed before introducing the helium gas.
For this reason, if the gas generated during the initial charge is released and the helium gas is introduced using the technique disclosed in JP 2002-117901 A, a step of temporarily sealing the pouring hole, a step of performing the initial charge, a step of removing the temporary seal and a step of introducing the helium gas need to be performed in this order.
As mentioned above, it is impossible to efficiently perform the step of manufacturing the sealed battery by a conventional technique. As a result, many steps need to be performed to manufacture the sealed battery, which leads to a high cost required to manufacture the sealed battery by the conventional technique.